We present an experimental method that nondestructively, relatively quickly, and reproducibly develops data necessary for finite-difference calculations of liquid-vapor diffusivities for water contents between approximately 1% and any intermediate value of interest. Diffusivity functions for five different soils, ranging in texture from fine sands to a clay loam, were determined. Vapor adsorption and transport mechanisms are discussed in the context of the liquid-vapor diffusivity function, using experimentally measured vapor adsorption isotherms. Conductivities calculated from results of experiments conducted using thermocouple psychrometers to nondestructively measure suction heads in a clay loam during the flow process are also presented.